EP0703934B1 - Process for producing decorative multiple-layer varnish coatings - Google Patents

Description

The invention relates to a method for producing decorative Multicoat paint systems of the type waterborne basecoat / clearcoat.

A large number of waterborne basecoats have become known which, because of their outstanding properties as binders, contain aqueous polyurethane dispersions. The polyurethane resins on which the polyurethane dispersions are based can be chain-extended in a wide variety of ways.
WO-A-94 13723 describes stone chip-resistant multi-layer coatings. For example, EP-A-0 089 497, EP-A-0 228 003, DE-A-36 28 124 and EP-A-0 512 524 describe waterborne basecoats which contain, as binders, aqueous polyurethane dispersions which are chain-extended by isocyanate-functional prepolymers can be produced with polyamine and / or polyol.

DE-A-39 15 459 and DE-A-42 24 617 provide examples of Waterborne basecoats containing aqueous polyurethane dispersions as binders contain isocyanate functional by chain extension Prepolymer can be made with water.

Examples of water-based paints based on water Polyurethane dispersions caused by chain extension from opposite PU prepolymers containing reactive, active hydrogen polyisocyanates can be made with polyisocyanates can be found in DE-A-39 03 804 and DE-A-40 01 841.

Using those based on known polyurethane dispersions formulated water-based paints are multi-layer paints in need of improvement with regard to their resistance to Condensation. Are the known polyurethane dispersions as Sole binder used in aqueous effect basecoats, that is Effect formation compared to at least one other cobinder containing aqueous effect basecoats less favorable.

EP-A-0 163 214 describes aqueous self-crosslinkable Polyurethane dispersions with preferably lateral siliconate groups. The The PU dispersions are produced and stored under conditions which deliberately prevents the siliconate groups from reacting with one another. After application, the binders crosslink by condensing the Silicate groups with formation of siloxane bridges.

Other aqueous solutions or dispersions of polyurethanes with Suitable reactive silicone groups are crosslinked from EP-A-0 315 006 known. The binders described there are by Reaction of isocyanate groups of isocyanate prepolymers with Amino groups built, d. H. there is a chain extension over Amino groups. In the manufacture of the binders a large amount Water added, so that due to the law of mass action practical no siloxane bridges are created.

Both EP-A-0 163 214 and EP-A-0 315 006 are not Notes indicate that the binders described there are suitable are for the production of water-based paints.

The object of the present invention is to provide a Process for the production of decorative multi-layer coatings from Waterborne basecoat / clearcoat type with improved condensation resistance, where aqueous polyurethane resins as binders in the water-based paints be used.

The object is solved by the subject matter of claim 1.

That used as a binder in the process according to the invention Aqueous polyurethane resin used in the water-based paint contains 5 to 200 mEqu (milliequivalents) on ionic groups, in ionic groups convertible groups and / or hydrophilic groups per 100 g of solid resin.

Are the groups which can be converted into ionic groups acidic groups, or if the ionic groups are anionic, they are preferably above 15 and below 100, particularly preferably above 18 and below 60 mEqu / 100 g solid resin in front.

If the groups that can be converted into ionic groups are basic groups, or if the ionic groups are cationic, they are preferably above 30 and below 150, particularly preferably above 45 and below 100 mEqu / 100 g Solid resin before.

In the case of the hydrophilic groups, the 5 to 200 mEqu relate to the lowest molecular weight components of such groups, for example on alkylene oxide units in polyalkylene oxide groups, e.g. on Ethylene oxide units in polyethylene oxide groups (such units are also called repetition units).

Examples of ionic and. Contained in the aqueous polyurethane resin result in groups which can be converted into ionic groups and hydrophilic groups derive from the following description which describes the preparation of the aqueous Polyurethane resin concerns.

1) Herstellung eines linearen oder verzweigten, nicht gelierten, ionische Gruppen, zur Ionenbildung befähigte Gruppen und/oder hydrophile Gruppen enthaltenden sowie isocyanatfunktionellen PU-Prepolymeren in einem organischen Lösemittel oder in Abwesenheit von Lösemitteln,

2) Umsetzung der freien Isocyanatgruppen des PU-Prepolymeren mit einer oder mehreren Verbindungen der allgemeinen Formel ((H-X-)_nR)_aSi(OR')_b(R")_c mit X = 0, S, NH oder NR'^v, bevorzugt NH oder NR'^v,
R = ein bifunktioneller, trifunktioneller oder tetrafunktioneller, bevorzugt bifunktioneller organischer Rest mit einem Molekulargewicht von 13 bis 500, bevorzugt (Ar)alkylen mit 1 bis 12 C-Atomen, besonders bevorzugt Alkylen mit 1 bis 12 C-Atomen,
R' = C₁- bis C₈-Alkyl oder C(O)R''', bevorzugt C₁- bis C₄-Alkyl,
R'' = R''' = C₁- bis C₁₀-Alkyl, wobei R'' und R''' gleich oder verschieden sein können,
R'^v = C₁- bis C₈-Alkyl,
a = 1, 2 oder 3, bevorzugt 1,
b = 1, 2 oder 3, bevorzugt 2 oder 3,
c = 0, 1 oder 2,
n = 1 bis 3, bevorzugt 1 oder 2, besonders bevorzugt 1
wobei mehrere Reste R', R'' und R''' gleich oder verschieden sind und worin die Summe aus a plus b plus c vier ergibt,
gegebenenfalls im Gemisch mit einem oder mehreren NH₂- und/oder NH-Gruppen tragenden Alkanolaminen mit einer OH-Funktionalität von mindestens 1, wobei die Mengenanteile der einzelnen Edukte so gewählt werden, daß das fertige Polyurethanharz die vorstehend angegebenen Spezifikationen aufweist, und

3) Überführung des gegebenenfalls neutralisierten Reaktionsproduktes in eine wäßrige Dispersion durch Zusatz von Wasser.

The aqueous polyurethane resin with lateral and / or terminal hydroxyl and / or R'O groups bonded to silicon can be produced, for example, by:

1) preparation of a linear or branched, non-gelled, ionic groups, groups capable of ion formation and / or hydrophilic groups and isocyanate-functional PU prepolymers in an organic solvent or in the absence of solvents,

2) reaction of the free isocyanate groups of the PU prepolymer with one or more compounds of the general formula ((HX-) _n R) _a Si (OR ') _b (R ") _c with X = 0, S, NH or NR ' ^v , preferably NH or NR' ^v ,
R = a bifunctional, trifunctional or tetrafunctional, preferably bifunctional organic radical with a molecular weight of 13 to 500, preferably (ar) alkylene with 1 to 12 C atoms, particularly preferably alkylene with 1 to 12 C atoms,
R '= C ₁ to C ₈ alkyl or C (O) R''', preferably C ₁ to C ₄ alkyl,
R '' = R '''= C ₁ to C ₁₀ alkyl, where R''andR''' can be the same or different,
R ' ^v = C ₁ to C ₈ alkyl,
a = 1, 2 or 3, preferably 1,
b = 1, 2 or 3, preferably 2 or 3,
c = 0, 1 or 2,
n = 1 to 3, preferably 1 or 2, particularly preferably 1
where several R ', R''andR''' are the same or different and the sum of a plus b plus c is four,
optionally in a mixture with one or more NH ₂ - and / or NH groups-bearing alkanolamines with an OH functionality of at least 1, the proportions of the individual starting materials being chosen so that the finished polyurethane resin has the specifications given above, and

3) Transfer of the optionally neutralized reaction product into an aqueous dispersion by adding water.

When transferring the possibly neutralized Reaction product in an aqueous dispersion, the water to the resin are given. It is also possible to add the resin to the water. It is essential that such an amount of water within a short time is added, which is sufficient to further react by Prevent hydrolysis of formed HOSi groups. The water addition takes place in more than ten times the stoichiometric excess of Hydrolysis of the R'OSi groups necessary amount of water. The is preferred at least 50-fold stoichiometric excess is added. Especially the water is preferably added in such an amount that at least half of those used to produce the aqueous Polyurethane dispersion required amount of water is added all at once. By adding the sufficient amount of water, an under Water condensation of the condensation of hydrolysis HOSi groups formed to form siloxane bridges are largely avoided, i.e. an aqueous dispersion of a polyurethane resin is obtained which is practically free of siloxane bridges and the R'OSi and / or HOSi groups in an amount sufficient for crosslinking.

Any solvent that may be present can be removed from the aqueous dispersion optionally distilled off.

In the production of the aqueous polyurethane resin, the proportions of the individual starting materials are selected and the reaction is carried out in such a way that the finished polyurethane resin 10 to 400 mmol, preferably 20 to 300 mmol, particularly preferably 40 to 200 mmol, of lateral and / or terminal hydroxyl bonded to silicon - and / or R'O groups, wherein
R '= C ₁ to C ₈ alkyl or C (O) R''', and
R '''= C ₁ to C ₁₀ alkyl
mean, per 100 g of solid resin, contains a number average (Mn) of molecular weight from 2500 to 120,000, a hydroxyl number from 0 to 150, preferably above 1 and below 100 mg KOH / g, based on solid resin, with hydroxyl groups bonded to silicon in the calculation not be counted in the OH number, and has a content of ionic, ionic groups and / or hydrophilic groups of 5 to 200 mEqu per 100 g of solid resin.

As an alternative to the sequential described above Manufacturing process using NCO prepolymers can manufacture the R'OSi-functionalized polyurethane resin also in a so-called One-step processes are carried out, i.e. the above Process steps 1) and 2) described can be carried out simultaneously be made by the reactants needed there at the same time be implemented.

When selecting the reactants, make sure that the functional groups -XH not affected in their reactivity become.

The production of the, for example in process step 1) linear or branched, non-gelled ionic groups, for Groups capable of ion formation and / or containing hydrophilic groups as well as isocyanate-functional PU prepolymers, hereinafter also referred to as NCO groups called containing polyurethane prepolymer, can for example, by implementing one or more Compounds with at least two groups reactive toward isocyanate, in particular one or more polyols, preferably diols, with one or more organic polyisocyanates, preferably diisocyanates and with one or more compounds with more than one, preferred two groups reactive with isocyanate groups and at least one ionic group, group capable of ion formation and / or hydrophilic group.

a) mindestens einer linearen oder verzweigten Verbindung, die mindestens zwei gegenüber Isocyanat reaktive Gruppen trägt mit einem mittleren Molekulargewicht von 60 bis 10000, bevorzugt 60 bis 6000,

b) mindestens einem organischen Polyisocyanat, insbesondere Diisocyanat,

c) mindestens einer Verbindung mit mehr als einer mit Isocyanat reaktiven Gruppe, und mindestens einer ionischen Gruppe, zur Ionenbildung befähigten Gruppe und/oder hydrophilen Gruppe, mit einer zahlenmittleren Molmasse (Mn) bis zu 10000, bevorzugt bis zu 2000, in einem NCO/OH-Verhältnis von Ober 1 bis 4 : 1.

For example, a polyurethane prepolymer containing NCO groups that can be used as a starting product for the production of the PU dispersion can be produced by reaction in an anhydrous environment of

a) at least one linear or branched compound which carries at least two isocyanate-reactive groups with an average molecular weight of 60 to 10,000, preferably 60 to 6000,

b) at least one organic polyisocyanate, in particular diisocyanate,

c) at least one compound having more than one isocyanate-reactive group, and at least one ionic group capable of ion formation and / or hydrophilic group, with a number-average molecular weight (Mn) up to 10,000, preferably up to 2,000, in an NCO / OH ratio from upper 1 to 4: 1.

It is preferably the aforementioned linear or branched compound of component a) by at least one polyol the basis of one or more polyethers, polyesters, polyurethanes and / or polycarbonates, with at least two OH groups in the molecule and a number average molecular weight (Mn) of 600-10,000, preferred over 1,000 and under 5,000, possibly with the use of one or several at least difunctional low molecular weight alcohols and / or amines and / or amino alcohols with a molecular weight below 600, preferably less than 400.

All manufacturing processes for polyurethane prepolymers containing NCO groups can be carried out as a single or multi-stage process become.

The PU prepolymer containing isocyanate groups preferably has one Content of urethane - (- NHCOO-) and possibly urea - (- NHCONH) Groups between 10 and 300 milliequivalents per 100 g of solid resin.

The aqueous polyurethane dispersion can be displayed at any stage be carried out without organic solvents.

The PU prepolymer containing NCO groups for the production of Component a) used compounds can, for example linear or branched polyol component, e.g. Be diols. It deals These are, for example, polyols familiar to the person skilled in the art based on the Field of PU chemistry. Examples are e.g. in the DE-A-42 28 510. If you start from a linear diol component from, can be used to achieve branching of the polymer Polyols with a functionality of 3 or more can be added. The amount should be chosen so that no gel formation during synthesis of the PU prepolymer containing NCO groups occurs.

Low-molecular weight may optionally be present in component a) Connections are used. It is particularly about Alcohols and amines. Examples are those from polyurethane chemistry known in the sense of an isocyanate addition reaction at least difunctional hydroxyl and / or amino groups Compounds of less than 600, preferably less than 300 Molecular weight. As a connection come both in the sense of Isocyanate addition reaction difunctional compounds as well at least trifunctional compounds or any mixtures of such compounds.

Component b) can be used for the production of the polyurethane dispersion any organic polyisocyanates, e.g. Diisocyanates used become. It can be aliphatic, cycloaliphatic, aromatic or araliphatic, as well as sterically hindered isocyanates become. For example, ether or ester groups can also be used containing polyisocyanates, e.g. Diisocyanates are used. Examples of suitable diisocyanates are hexamethylene diisocyanate, 1-isocyanatomethyl-5-isocyanato-1,3,3-trimethylcyclohexane, Bis- (4-isocyanatocyclohexyl) methane, Bis (4-isocyanato-phenyl) methane and Tetramethylxylylene.

If necessary, even more functional can be used in small proportions Isocyanates such as Biuret or isocyanurate type polyisocyanates, or products made by reacting an excess of diisocyanate of polyols obtained can be added.

worin Q' Wasserstoff oder C₁-C₈-Alkyl ist. Die bevorzugtesten Verbindungen sind alpha,alpha-Dimethylolpropionsäure und alpha,alpha-Dimethylolbuttersäure.As component c) it is possible, for example, to use low-molecular, for example monomeric, compounds which contain more than one, preferably two or at least two groups reacting with isocyanate groups and at least one ionic group, group capable of ion formation and / or hydrophilic group. Anionic or anion-forming groups are preferred. Suitable groups reacting with isocyanate groups are in particular hydroxyl groups and primary and secondary amino groups. Examples of suitable acidic groups capable of forming anions are carboxyl, phosphoric acid and sulfonic acid groups. Possible basic groups which can be converted into cations are, for example, primary, secondary and tertiary amino groups or onium groups, such as quaternary ammonium, phosphonium and / or tertiary sulfonium groups. The preferred anionic groups to be introduced are carboxyl groups; they can be introduced, for example, by using hydroxyalkanecarboxylic acids of the following general formula as component c): (HO) _x Q (COOH) _y wherein
Q represents a straight or branched hydrocarbon radical with 1 to 12 carbon atoms and
x and y each represent 1 to 3. Examples include citric acid and tartaric acid. Preferred carboxylic acids are those in which x = 2 and y = 1. Examples of this are described in US-A-3,412,054. A preferred group of dihydroxyalkanoic acids are alpha, alpha-dimethylolalkanoic acids of the general formula

wherein Q 'is hydrogen or C ₁ -C ₈ alkyl. The most preferred compounds are alpha, alpha-dimethylol propionic acid and alpha, alpha-dimethylol butyric acid.

Further examples of dihydroxyalkanoic acids that can be used are Dihydroxypropionic acid, dimethylol acetic acid, dihydroxysuccinic acid or dihydroxybenzoic acid.

Examples of amino group-containing acids that can be used are alpha, alpha-diamino-valeric acid, 3,4-diaminobenzoic acid, 2,4-diaminotoluene-sulfonic acid- (5) and 4,4-diamino-di-phenyl ether sulfonic acid.

Acidic polyesters as described in DE-A-39 03 can also be used as component c) 804 are used. These have polyester preferably a molecular weight of 300 to 2000, a hydroxyl number from 56 to 374 and an acid number from 28 to 187.

Component c) can also be ionic or ionic groups convertible groups containing polyurethane polyols are used.

HO - X - Y - R⁶ HNR³ - X - Y - R⁶ worin
R = der Rest, der sich aus einer Isocyanatkomponente ergibt, z.B. aus Isocyanaten, wie sie vorstehend genannt wurden,
R³ = H, lineares oder verzweigtes C₁-C₈-Alkyl,
R⁶ = C₁-C₁₂-Alkyl, bevorzugt unsubstituiertes C₁-C₄-Alkyl,
X = ein Rest, wie er durch Entfernen des endständigen Sauerstoffatoms aus einer Polyalkylenoxidkette mit 5 bis 90, vorzugsweise 20 bis 70 Kettengliedern erhalten wird, wobei die Kettenglieder zumindest zu 40 %, vorzugsweise zu 65 % aus Ethylenoxideinheiten bestehen und die neben Ethylenoxideinheiten beispielsweise auch Propylenoxid-, Butylenoxid- oder Styroloxideinheiten darstellen können,
Y = - 0 - oder - NR⁶ -, wobei R⁶ wie vorstehend definiert ist.Component c) can also comprise nonionic hydrophilic polyols. These are, for example, compounds which have polyether chains with built-in ethylene oxide units. They are compounds with one or two hydrogen atoms which are reactive toward isocyanates and which carry, for example, polyether chains containing ethylene oxide in the side chain or mixtures thereof. These are, for example, compounds of the general formula

HO - X - Y - R ⁶ HNR ³ - X - Y - R ⁶ wherein
R = the radical resulting from an isocyanate component, for example from isocyanates as mentioned above,
R ³ = H, linear or branched C ₁ -C ₈ alkyl,
R ⁶ = C ₁ -C ₁₂ alkyl, preferably unsubstituted C ₁ -C ₄ alkyl,
X = a residue such as is obtained by removing the terminal oxygen atom from a polyalkylene oxide chain with 5 to 90, preferably 20 to 70, chain links, the chain links consisting at least 40%, preferably 65%, of ethylene oxide units and, in addition to ethylene oxide units, for example also propylene oxide - can represent butylene oxide or styrene oxide units,
Y = - 0 - or - NR ⁶ -, where R ^{6 is} as defined above.

The preparation of compounds II to IV can e.g. analogous to US-A-3 920 598, US-A-3 905 929, US-A-4 190 566 or US-A-4 237 264.

The anionic, cationic or non-ionic groups of Component c) serve to stabilize the aqueous dispersion. It Ionic and non-ionic groups can be used together. Stabilization by ionic groups is preferred, in particular preferably anionic groups.

To produce an anionic urethane prepolymer, the Dihydroxycarboxylic acids preferred. The is particularly preferred Dimethylolpropionic. Component c) is preferred in an amount from about 0.4 to about 7.5% by weight, particularly preferably from about 0.8 to 5.0 % By weight (calculated as carboxyl group COOH), based on the amount used Urethane prepolymer (solid resin) used. If the amount of carboxyl groups is below about 0.4% by weight, it is difficult to obtain a stable emulsion manufacture. On the other hand, if the amount exceeds 7.5% by weight, reinforced the hydrophilic property, which makes the emulsion highly viscous and reduces the water resistance of the coating.

The amounts of a), b) and c) are chosen so that during the implementation a reaction product with lateral and / or terminal NCO groups arises, i.e. an excess of polyisocyanate is used. you can work with an NCO to OH ratio of over 1 to 4: 1, the range from 1.1 to 2: 1 is preferred, particularly preferably from 1.1 to 1.7: 1. It is preferably a polyurethane with less as 280 mEquivalents - NHCOO - per 100 g solid resin. The The reaction product can have a branched structure, it is preferred in the general but linear structure with terminal NCO groups.

The polyurethane prepolymer containing NCO groups is mixed with one or more compounds of the general formula ((HX-) _n R) _a Si (OR ') _b (R'') _c with X = 0, S, NH or NR ' ^v , preferably NH or NR' ^v ,
R = bifunctional to tetrafunctional, preferably bifunctional organic radical with a molecular weight of 13 to 500, preferably (ar) alkylene with 1 to 12 C atoms, particularly preferably alkylene with 1 to 12 C atoms,
R '= C ₁ to C ₈ alkyl or C (O) R''', preferably C ₁ to C ₄ alkyl,
R "= R"'= C ₁ to C ₁₀ alkyl,
R ' ^v = C ₁ to C ₈ alkyl,
a = 1, 2 or 3, preferably 1,
b = 1, 2 or 3, preferably 2 or 3,
c = 0, 1 or 2,
n = 1 to 3, preferably 1 or 2, particularly preferably 1
and wherein the sum of a plus b plus c results in four, optionally in a mixture with alkanolamines carrying one or more NH ₂ and / or NH groups and having an OH functionality of at least 1, to form an ionic group, groups capable of ion formation and / or implemented polyurethane resin containing lateral and / or terminal R'O groups bonded to hydrophilic groups.

The compounds of the general formula (I) are silane derivatives which have active hydrogen-containing groups of the (HX-) _n R-type which are capable of addition to isocyanate groups. As active hydrogen-containing functional groups HX-, amine groups are preferred. n has values from 1 to 3, preferably n assumes the value 1. The radical R is a bifunctional to tetrafunctional, preferably bifunctional, organic radical which can carry chemically inert groups or substituents and has a molecular weight of 13 to 500. The radical R is preferably a bifunctional (ar) alkylene radical with 1 up to 12 carbon atoms. An alkylene radical having 1 to 12 carbon atoms is particularly preferred as the radical R.

Furthermore, the silane derivative of the general formula (I) contains 1 to 3, preferably 2 or 3 groups R'O groups bonded to silicon, where R 'preferably has the meaning of C ₁ -C ₈ -alkyl.

Some preferred examples of compounds (I) are beta-aminoethyltriethoxysilane, gamma-aminopropyltriethoxysilane, gamma-aminopropyltrimethoxysilane, gamma-aminopropylethyldiethoxysilane, gamma-aminopropylphenyldiethoxysilane, gamma-aminopropyltrimethoxysilane, delta-aminobutyltriethoxysilane, delta-aminobutylethyldiethoxysilane, N- (2-aminoethyl-3-aminopropyl) trimethoxysilane, N-2-aminoethyl-3-aminopropyl-tris (2-ethylhexoxy) silane, 6- (Amlnohexylaminopropyl) trimethoxysilane, N-aminoethyl-3-aminopropylmethyl dimethoxysilane called.

The implementation of the NCO-functional polyurethane prepolymer to the R'OSi-functionalized Polyurethane resin is done under complete Consumption of the HX groups of the compounds I. Are preferred Isocyanate groups and HX groups stoichiometrically in a 1: 1 ratio brought together to react. But it is also possible that To carry out reaction with an excess of isocyanate groups. The remaining isocyanate groups can be used for further build-up reactions, for example by reaction with water, hydrazine, Carboxylic acid hydrazides, polyols or amines can be used.

The lateral and / or terminal R'O groups-bonded polyurethane resin can have hydroxyl groups. If this is desired, the polyurethane prepolymer containing NCO groups is used in the preparation of the R'OSi-functionalized polyurethane resin with at least one compound of the general formula I and with at least one alkanolamine carrying NH ₂ and / or NH groups with an OH -Functionality implemented by at least 1. The reaction takes place with complete consumption of the HX groups of the compounds I and the NH groups of the alkanolamine. The isocyanate groups of the NCO-functional PU prepolymer are preferably reacted with the HX groups of I and the NH groups of the alkanolamine in a stoichiometric ratio. The alkanolamine and the compound I can be reacted in a mixture or in succession with the NCO-functional polyurethane prepolymer.

The alkanolamines carrying NH ₂ and / or NH groups and having an OH functionality of at least 1 are compounds which can serve as suppliers for hydroxyl groups in the polyurethane resin dispersion. The NH or NH ₂ groups of the alkanolamines have a significantly higher reactivity compared to their OH groups compared to the isocyanate groups of the NCO-functional PU prepolymer, ie the NH groups react preferentially with the isocyanate groups to form urea.

Examples of suitable alkanolamines with an OH functionality of at least 1 are monoalkanolamines and dialkanolamines, e.g. Diethanolamine, N-methylethanolamine, diisopropanolamine, N-ethylisopropanolamine, Monoisopropanolamine, ethanolamine, 2,2-aminoethoxyethanol, Monoethylethanolamine, butylethanolamine, Cyclohexylethanolamine, 3-aminopropanol, 2-aminobutanol-1.

Instead of the alkanolamines carrying NH ₂ and / or NH groups, it is also possible to use other monofunctional compounds which are reactive toward NCO groups, for example monoamines and / or monoalcohols having C-6 to C-30 alkyl radicals. Fatty amines and / or fatty alcohols with more than 12 carbon atoms are preferred. In this case, polyurethane resins bearing R'O groups and containing no hydroxyl groups are obtained. Of course, monoamines and / or monoalcohols can also be used in a mixture with the alkanolamines carrying NH ₂ and / or NH groups. In this way, the OH number of the resulting lateral and / or terminal polyurethane resin having R'O groups bonded to silicon can be set as desired in the range from 0 to 100.

An essential step in the manufacture of the aqueous Polyurethane dispersion based on the lateral and / or terminal Silicon-bound R'0 and / or hydroxyl groups Polyurethane resin consists of the R'OSi-functionalized PU prepolymer, which optionally has hydroxyl groups within a short time such an amount of water is added that is sufficient is another reaction of the HOSi groups formed by hydrolysis to prevent. The water is added in more than ten times stoichiometric excess for hydrolysis of the R'Osi groups necessary amount of water. At least 50 times is preferred stoichiometric excess added. This is particularly preferably done Add water in such an amount that at least half of the water Production of the aqueous polyurethane dispersion required amount of water is added at once. By adding the sufficient amount of water becomes a condensation of water that runs off Hydrolysis largely formed HOSi groups to siloxane bridges avoided, i.e. an aqueous dispersion of a Polyurethane resin that is practically free of siloxane bridges and that R'OSi and / or HOSi groups in a sufficient for networking Quantity contains.

The polyurethane resin has ionic groups capable of ion formation Groups and / or hydrophilic groups. Contains the polyurethane resin Groups capable of ion formation are identified with a suitable connection, e.g. a neutralizing agent, whole or partially converted into the corresponding salts. This can be done in all Stages of the synthesis described above happen, whereby to note that the selection of those used for salt formation Connections are made so that they are during the synthesis behave chemically inert. Those for salt formation are preferred used connections such as Neutralizing agent together with added to the water.

Preferred ion-forming groups are those which form anions are qualified. Examples of such groups are above in the Synthesis of the PU prepolymer containing NCO groups described. to Conversion to anions then serves as a base, e.g. an amine, preferred a tertiary amine. Suitable tertiary amines are e.g. Trialkylamines like Trimethylamine, triethylamine, triisopropylamine, tri-n-propylamine and Tri-n-butylamine; N-alkylmorpholines such as N-methylmorpholine and N-ethylmorpholine; N-dialkylalkanolamines, such as N-dimethylethanolamine, N-diethylethanolamine and N-dimethylisopropanolamine and mixtures of at least two of these connections.

If the polyurethane resin contains cation-forming groups, then preferably one or more acids used for ion formation. Suitable acids are e.g. Phosphoric acid or acidic phosphoric acid esters, or organic carboxylic acids such as formic acid, acetic acid, Propionic acid, acrylic acid, hydroxycarboxylic acids such as lactic acid, Dimethylolpropionic acid or citric acid, or dicarboxylic acids such as Malonic acid, glutaric acid or oxalic acid. Mixtures of Acids are used. But it is also one Quaternization reaction with alkylating agents, e.g. the Reaction with alkyl halides or epoxides possible.

The implementation of the PU prepolymer used to build the NCO used components as well as the further implementation to the R'OSi functionalized Polyurethane resin is made in an anhydrous environment for example at temperatures of 20 to 140 ° C, preferably between 40 and 100 ° C. It can be worked solvent-free or it is in the Those skilled in the art are suitable per se for polyurethane synthesis organic solvents worked. Can be used as a solvent water-miscible solvents or non-water-miscible solvents be used. In general, it is advantageous to use such solvents to be used at every stage of the manufacture of the PU dispersion (for example after their completion) can be removed, for example by distillation, if appropriate with reduced Print.

Examples of suitable solvents are ketones, e.g. Acetone, Methyl ethyl ketone, methyl isobutyl ketone; N-alkyl pyrrolidones, e.g. N-methylpyrrolidone; Ethers such as diethylene glycol dimethyl ether, Dipropylene glycol dimethyl ether, or also cyclic urea derivatives, such as 1,3-dimethyl-3,4,5,6-tetrahydro-2 (1H) pyrimidinone.

The solvent-free or organic solution Polyurethane resin is added by adding sufficient amounts of water to the transferred aqueous phase. The result is a finely divided one Polyurethane dispersion with an average particle size greater than 10 and less than 2000 nm, preferably above 50 and below 500 nm Distribution can be monomodal or bimodal, preferably monomodal.

In general, it is not necessary to transfer the used To use polyurethane resins in aqueous dispersions emulsifiers. However, this does not exclude that emulsifiers are more ionic and nonionic Art can be added to emulsify too facilitate, and possibly the number of ionizable groups reduce.

In the production of the polyurethane dispersion, the starting materials are reacted with one another in such amounts that the binder qualities desired by the person skilled in the art are achieved, such as, for example, water dispersibility, viscosity behavior, film formation properties and storage stability. Properties, such as hardness and weatherability, of coatings obtained from the dispersions can also be influenced by the choice of the type and the amount of the components. The choice of the type and the amount of the components can easily be determined by the person skilled in the art on the basis of the teaching shown here, if appropriate on the basis of routine experiments. Overall, the proportions of the individual starting materials are preferably selected and the reaction is carried out such that the polyurethane resin on which the polyurethane dispersion is based has a number average molecular weight (Mn) of 2500 to 120,000, a content of 10 to 400, preferably 20 to 300 mmol, particularly preferably 40 to 200 mmol of lateral and / or terminal silicon-bonded hydroxyl and / or R'O groups, in which
R '= C ₁ to C ₈ alkyl or C (O) R''', and
R '''= C ₁ to C ₁₀ alkyl
mean, per 100 g of solid resin, a hydroxyl number from 0 to 150, preferably above 1 and below 100 mg KOH / g, based on solid resin, hydroxyl groups bonded to silicon are not included in the calculation of the OH number, and an ionic content , convertible into ionic groups and / or hydrophilic groups of 5 to 200 mEqu per 100 g of solid resin.

The production of the aqueous PU dispersion based on the lateral and / or terminal hydroxyl and / or R'O groups bonded to silicon load-bearing polyurethane resin can be made by known methods. For example, it is possible to submit the neutralized resins and to be mixed with water while dispersing well. As well can optionally contain the neutralizing agent water phase submitted and incorporated the resin with stirring. Likewise continuous operation possible, i.e. it will be known in Aggregates, e.g. a rotor-stator mixer, resin, water at the same time and neutralizing agent mixed homogeneously.

The pH of the resulting polyurethane dispersion can for example set to a value between 5 and 10. It the components create a finely divided opaque to milky cloudy aqueous dispersion.

The preferred anionic PU dispersions have a Acid number from 5 to 90 (based on the solids), preferably above 10 and under 50 on. The solid is between 25 and 65% by weight, preferably above 35 and below 60% by weight. The number average molecular weight (Mn) of the polyurethane resins contained in the PU dispersions for example 2500 to 120000, the lower limit preferably being 4000, particularly preferably at 10000 and the upper limit at up to 50,000 lies.

Any solvents contained in the polyurethane dispersions can be removed by distillation if desired. This can happen under reduced pressure.

The waterborne basecoats made from the PU dispersions are self-crosslinking. The PU resins on which the PU dispersions are based have hydroxyl numbers between 0 and 100, preferably between 0 and 60 mg KOH / g, with hydroxyl groups bonded to silicon at the Calculation of the OH number should not be counted. Should they in self-crosslinking method used according to the invention Waterborne basecoats should be accessible for additional external crosslinking the hydroxyl number of the polyurethane resins is preferably in the upper range Value range.

The PU dispersion is used to produce the self-crosslinking water-based paints for example pigments, other binders, additives and optionally small amounts of solvents added.

The waterborne basecoats can be used in addition to Polyurethane resin dispersion one or more other different Contain binders. This can be achieved, for example synergistic effects. Examples of other binders are conventional film-forming water-soluble or water-thinnable resins, such as water-thinnable polyester resins, water-dilutable polyacrylate resins and / or other types water-borne polyurethane resins. It can be reactive or act non-functional resins. The amount of resins added can 0 to 75% by weight, preferably 0 to 50% by weight of the total Resin solids amount. 0 to 30% by weight are particularly preferred. In In this context, resin solids mean the sum of all binders without the possibly existing crosslinker share for the if necessary additionally desired external networking.

The specification and the proportion of additional binders are chosen so that there is preferably a mixture that on average a content of ionic and / or convertible into ionic groups Has hydrophilic groups of 5 to 200 mEqu per 100 g of solid resin. Anionic groups are preferred.

Usable water-dilutable polyesters are, for example, those with free carboxyl groups, i.e. High acid number polyester. There are basically two methods known, the required carboxyl groups in insert the resin system. The first way is esterification to terminate at the desired acid number. With this procedure the incorporation of sterically hindered carboxyl groups, for example by condensation with dimethylolpropionic acid, prefers. After neutralization with bases, the so obtained Polyester soluble in water. The second option is Formation of partial esters of di- or polycarboxylic acids with hydroxyl-rich polyesters with low acid number. For this reaction anhydrides of dicarboxylic acids are usually used, which under mild conditions to form a free carboxyl group be reacted with the hydroxyl component.

The water-dilutable polyacrylate resins that can be used can be as well the polyester resins described above contain free carboxyl groups. These are, for example, acrylic or methacrylic copolymers, and the carboxyl groups come from the proportions of acrylic or Methacrylic acid.

Additional polyurethane dispersions include, for example to understand that are described in DE-A-36 28 125. There are anionically stabilized PU dispersions, which are produced by the implementation of Polyols, diisocyanates, ionic compounds and Chain extension with amines can occur. Furthermore can also PU dispersions stabilized by non-ionic hydrophilic groups the self-crosslinking used in the process according to the invention Waterborne basecoats are added.

The water-dilutable polyester or polyurethane resins can also acrylated in dispersions by suitable polymerization processes or be grafted. Examples of usable acrylated Polyurethane dispersions are described in DE-A-41 22 265.

Another group of aqueous dispersions that the in added water-based paints according to the invention can be, are those described in DE-A-36 28 124 Dispersions based on ionic epoxy groups Polycondensates made with copolymerizable unsaturated monomers be implemented.

When adding other binders, it goes without saying that additional ionically stabilized resins and dispersions only together can be used with similarly charged ionic dispersions in order not to negatively affect stability.

To prepare those which can be used in the process according to the invention per se Self-crosslinking waterborne basecoats can, if an additional External networking is desired, such as different crosslinkers for example formaldehyde condensation resins such as phenol-formaldehyde condensation resins and amine-formaldehyde condensation resins, as well blocked polyisocyanates are used. The crosslinkers can can be used individually and in a mixture. The mixing ratio Crosslinker to polyurethane resin is preferably 10:90 to 40:60, particularly preferably 20:80 to 30:70, in each case based on the Weight of solids. If in addition to the polyurethane resin dispersion of the invention other binders are used, refer to the above mixing ratios preferably on the whole Resin solids.

Amine resins suitable as crosslinkers include, for example, alkylated resins Condensates by the reaction of aminotriazines and amidotriazines be produced with aldehydes. According to known technical processes compounds containing amines or amino groups such as melamine, Guanamine, acetoguanamine, benzoguanamine, dicyandiamide or urea in Presence of alcohols, such as methanol, ethanol, propanol, or butanol Hexanol condensed with aldehydes, especially formaldehyde. The The reactivity of such amine resins is determined by the Degree of condensation, the ratio of the amine or amide components to Formaldehyde and the type of etherification alcohol used. Examples of such resins and their preparation are described in "Houben-Weyl, Methods of Organic Chemistry "1963, page 357. These products are commercially available.

Blocked polyisocyanates can also be used as crosslinking agents become. Any polyisocyanates can be used in the invention in which the isocyanate groups are reacted with a compound have been so that the blocked polyisocyanate formed against Hydroxyl groups and water is stable at room temperature elevated temperatures, for example in the range from about 90 to about 250 ° C, but reacts. When making the blocked Polyisocyanates can be any organic suitable for crosslinking Polyisocyanates are used. The isocyanates are preferred about 3 to about 36, especially about 8 to 15 carbon atoms contain. Examples of suitable diisocyanates are as above Component b) mentioned diisocyanates.

Polyisocyanates of higher isocyanate functionality are preferred, as used above under b). Examples of this are Tris (4-isocyanatophenyl) methane, 1,3,5-triisocyanatobenzene, 2,4,6-triisocyanatotoluene, 1,3,5-tris (6-isocyanatohexane) biuret, bis (2,5-diisocyanato-4-methylphenyl) methane and polymeric polyisocyanates, such as Dimers and trimers of diisocyanatotoluene. You can also Use mixtures of polyisocyanates.

Those considered as crosslinking agents in waterborne basecoats upcoming organic polyisocyanates can also be prepolymers that derived, for example, from a polyol. This will be done in more common Way polyols reacted with an excess of polyisocyanates, resulting in prepolymers with terminal isocyanate groups. The blocked polyisocyanates; which are used as crosslinkers can, with usual volatile monovalent blocking agents be blocked, as they are used in paint chemistry. Examples there are various alcohols, oximes, phenols, NH-functional ones Nitrogen heterocycles, such as pyrazole derivatives or triazole derivatives, Amines, beta-keto compounds and phthalimide. The polyisocyanates can in a molecule with the same or different blocking agents be blocked. Mixtures can also act as crosslinkers blocked polyisocyanates are used as well as polyisocyanates, which are blocked differently intramolecularly.

The self-crosslinking waterborne basecoats can also be used by those skilled in the art contain known polymer microparticles. It can be networked or uncrosslinked microparticles can be used. Examples of such Polymer microparticles are in EP-A-0 038 127 and EF-A-0 234 362 described.

Furthermore, those which can be used in the process according to the invention can be used self-crosslinking waterborne basecoats contain paint additives, for example rheology-influencing agents such as highly disperse Silicic acid, inorganic layered silicates or polymers Urea compounds. Also act as thickeners, for example water-soluble cellulose ethers such as hydroxyethyl cellulose, Methyl cellulose or carboxymethyl cellulose, as well as synthetic Polymers with ionic and / or associative groups such as Polyvinyl alcohol, poly (meth) acrylamide, poly (meth) acrylic acid, Polyvinyl pyrrolidone, styrene-maleic anhydride or ethylene-maleic anhydride copolymers and their derivatives or also hydrophobic modified ethoxylated polyurethanes or polyacrylates. Besides Anti-settling agents, leveling agents, light stabilizers, Anti-foaming agents, such as silicone-containing compounds; Wetting agents and adhesion-promoting substances are used. Under Wetting agents are also understood to be known paste resins which are used for better dispersing and grinding of the pigments can be used can. To accelerate the hardening, if necessary Catalysts are used, but it is also possible through to harden thermal energy without the use of a catalyst.

Customary coating solvents are suitable as solvents present in small quantities; these can come from the production of the binders or are added separately. Examples of such solvents are monohydric or polyhydric alcohols, for example propanol, butanol, hexanol; Glycol ethers or esters, for example diethylene glycol dialkyl ethers, dipropylene, each with C _1-6 alkyl, ethoxypropanol, butyl glycol; Glycols, for example ethylene glycol; Propylene glycol, and its oligomers, N-methylpyrrolidone and ketones such as methyl ethyl ketone, acetone, cyclohexanone; aromatic or aliphatic hydrocarbons, for example toluene, xylene or C ₆ -C ₁₂ linear or branched aliphatic hydrocarbons.

The self-crosslinking waterborne basecoats can have one or more inorganic and / or organic color and / or effect pigments and optionally additionally contain at least one filler.

Examples of effect pigments are metal pigments, e.g. out Aluminum, copper or other metals; Interference pigments such as metal oxide coated metal pigments, e.g. coated with titanium dioxide Aluminum, coated mica such as titanium dioxide-coated Mica and graphite effect pigments. Examples of color pigments and fillers are titanium dioxide, micronized titanium dioxide, Iron oxide pigments, carbon black, silicon dioxide, barium sulfate, micronized Mica, talc, kaolin, chalk, azo pigments, phthalocyanine pigments, Quinacridone pigments, pyrrolopyrrole pigments, perylene pigments.

The effect pigments are generally in the form of a commercially available submitted aqueous or non-aqueous paste, optionally with preferably water-dilutable, organic solvents and additives added and then with the aqueous binder under scissors mixed. Powdery effect pigments can initially be preferred water-dilutable organic solvents and additives to a paste are processed. Care should be taken that the platelet-shaped Effect pigments are not mechanically damaged when mixed.

Color pigments and / or fillers can, for example, in one part of the aqueous binder are rubbed. This can preferably Rub also in a special water-thinnable paste resin happen. An example of a waterborne basecoat according to the invention paste resin based on polyurethane can be found in DE-A-40 00 889. Grinding can be carried out in the usual way, the expert known units take place. After that, with the rest of the share of the aqueous binder or the aqueous paste resin to be finished Color pigment rubbing completed.

If paste resins are present in the coating agent, these add up when calculating the resin solids to binder plus any crosslinker present.

The waterborne basecoat is based on the preferred anionic stabilized, self-crosslinking lateral and / or terminal R'OSi- and / or polyurethane resin bearing HOSi groups it contains bases as neutralizing agents. Examples are ammonia or organic amines such as triethylamine, N-methylmorpholine, Amino alcohols such as dimethylisopropanolamine, dimethylethanolamine, 2-amino-2-methylpropanol-1.

The self-crosslinking waterborne basecoats, for example, have one Solids content of 10 - 50 wt .-%, it is for effect basecoats for example, preferably 15-30% by weight, for plain-colored basecoats it is preferably higher, for example 20-45% by weight. The Ratio of pigment to binder plus crosslinking agent if necessary plus possibly paste resin in the water-based lacquer for example between 0.03: 1 to 3: 1, for effect basecoats for example, it is preferably 0.06: 1 to 0.6: 1, for plain-colored ones Basecoats are preferably higher, for example 0.06: 1 to 2.5: 1, each based on the solid weight.

The solvent content of the water-based paints is preferably below 20 % By weight, particularly preferably less than 15% by weight, particularly preferred below 10% by weight.

The self-crosslinking waterborne basecoats can be prepared using customary methods be applied. They are preferred by spraying in a Dry layer thickness of 8 to 50 µm applied, for effect basecoats the dry layer thickness is, for example, preferably 10 to 25 µm, for plain-colored basecoats it is preferably higher, for example at 10 to 40 µm. The application is preferably carried out in the wet-on-wet process, i.e. after a flash-off phase, e.g. at 20 - 80 ° C, the Waterborne basecoats with a common clearcoat in one Dry layer thickness of preferably 30 - 60 µm overcoated and together with this at temperatures of, for example, 20 to 140 ° C below Condensation of the HOSi groups cross-linked to form siloxane bridges. The Drying conditions of the top coat layer (basecoat and clearcoat) depend on the clear coat system used. You can for example at 20 to 150 ° C. Are for repair purposes for example, temperatures of 20 to 80 ° C preferred. For purposes of Series paints are temperatures above 100 ° C, for example above 110 ° C preferred.

Basically, all known clearcoats or Transparent pigmented coating agent suitable. Here you can both solvent-based 1- or 2-component paints, water-borne clear coats, powder clear coats or by radiation curable clear coats are used.

Multicoat paint systems produced by the process according to the invention are applied to metallic substrates. The metallic substrates have an electrophoretically applied primer and one or more others Filler layers (primer surfacer). These layers are in the generally cured. However, the waterborne basecoat can also be applied uncrosslinked filler layers such as described in EP-A-0 238 037, can be applied wet-on-wet. In this case, the basecoat in general before applying a clear lacquer topcoat together with the Burned-in filler layer.

It is also possible to apply the waterborne basecoat directly, without further Intermediate layers on a baked or non-baked To apply electrocoat, like this for others known solvent-based or water-based basecoats is possible.

Those obtained using the method according to the invention Multicoat paint systems meet the current requirements in automotive painting. The method according to the invention is thus suitable for vehicle painting and refinishing, it can also be used in other areas, e.g. the plastic painting, in particular the painting of vehicle parts.

The manufactured by the inventive method Multi-layer painting has a good surface. Liability between the layers and the basecoat layer good and shows none even when exposed to damp conditions Delamination problems. The invention is particularly suitable for Use in automotive painting (serial and Refinishing).

Those according to the invention using the self-crosslinking Waterborne basecoats, which bind the lateral and / or terminal Contain R'OSi and / or HOSi groups-containing polyurethane resins, Multi-layer coatings produced are characterized by a excellent resistance to condensation.

Production example 1:

339 g of a polyester made from adipic acid, hexanediol and isophthalic acid (OH number 104) and 19 g of dimethylolpropionic acid are in 160 g of N-methylpyrrolidone dissolved and heated to 40 ° C. Then 125 g Isophorone diisocyanate added so that a reaction temperature of 80 ° C is not exceeded. It is held until an NCO content of 2% (based on solid resin) determined according to DIN 53 185 is.

Then 14.6 g of 3-aminopropyltriethoxysilane and 16.2 g of diethanolamine added. The reaction mixture is at 80 ° C held until no free NCO groups can be detected (Titration). 12.6 g of triethylamine are good for neutralization incorporated.

After adding the neutralized resin solution to 596 g of fully desalinated Water with vigorous stirring gives a finely divided aqueous solution Polyurethane dispersion.

Production example 2:

339 g of a polyester made from adipic acid, hexanediol and isophthalic acid (OH number: 104) and 19 g of dimethylolpropionic acid are in 160 g of N-methylpyrrolidone dissolved and heated to 40 ° C. Then 125 g Isophorone diisocyanate added so that a reaction temperature of 80 ° C is not exceeded. It is held until an NCO content of 2% (based on solid resin) determined according to DIN 53 185 is. Then 43.8 g of 3-aminopropyltriethoxysilane and 2.3 g of diethanolamine added. The reaction mixture is so long Maintained 80 ° C until no free NCO groups can be detected (Titration). 12.6 g of triethylamine are good for neutralization incorporated.

After the addition of 596 g of deionized water within 5 minutes a finely divided aqueous polyurethane dispersion is obtained.

Production Example 3:

339 g of a polyester made from adipic acid, hexanediol and isophthalic acid (OH number: 104) and 19 g of dimethylolpropionic acid are in 160 g of N-methylpyrrolidone dissolved and heated to 40 ° C. Then 125 g Isophorone diisocyanate added so that a reaction temperature of 80 ° C is not exceeded. It is held until an NCO content of 2% (based on solid resin) determined according to DIN 53 185 is. Then 42 g of 3-aminopropylmethyldiethoxysilane are added.

The reaction mixture is kept at 80 ° C. until there are no free ones NCO groups are more detectable (titration). For neutralization 12.6 g of triethylamine are worked in well. After the addition of 596 g demineralized water is obtained within 5 minutes finely divided aqueous polyurethane dispersion.

Production example 4:

339 g of a polyester made from adipic acid, hexanediol and isophthalic acid (OH number: 104) and 19 g of dimethylolpropionic acid are in 160 g of N-methylpyrrolidone dissolved and heated to 40 ° C. Then 118.3 g Trimethyl hexamethylene diisocyanate added so that a Reaction temperature of 80 ° C is not exceeded. It will be so long held until an NCO content of 2% (based on solid resin) determined according to DIN 53 185.

Then 33.6 g of 3-aminopropylmethyldiethoxysilane and 4.6 g of diethanolamine added. The reaction mixture is so long Maintained 80 ° C until no free NCO groups can be detected (Titration). After adding the resin solution to a mixture of 10.9 g N, N-dimethylisopropanolamine and 596 g of deionized water vigorous stirring gives a finely divided aqueous solution Polyurethane dispersion.

Production example 5:

339 g of a polyester made from adipic acid, hexanediol and isophthalic acid (OH number: 104) and 19 g of dimethylolpropionic acid are in 160 g of N-methylpyrrolidone dissolved and heated to 40 ° C. Then 125 g Isophorone diisocyanate added so that a reaction temperature of 80 ° C is not exceeded. It is held until an NCO content of 2% (based on solid resin) determined according to DIN 53 185 is. Then 35.4 g of 3-aminopropyldimethylethoxysilane are added.

The reaction mixture is kept at 80 ° C. until no free ones NCO groups are more detectable (titration). For neutralization 14.5 g of triethylamine are worked in well. After the addition of 596 g demineralized water is obtained within 5 minutes finely divided aqueous polyurethane dispersion.

Production example 6:

346 g of a polycaprolactone diol (OH number: 102) and 19 g Dimethylolpropionic acid are dissolved in 160 g of N-ethylpyrrolidone and heated to 40 ° C. Then 138 g of 1,3-bis (1-isocyanato-1-methylethyl) benzene (TMXDI) added so that a reaction temperature of 100 ° C is not exceeded. It is held until one NCO content of 2% (based on solid resin) determined according to DIN 53 185 is reached. Then 43.8 g of 3-aminopropyltriethoxysilane are successively and 2.3 g of diethanolamine were added.

The reaction mixture is kept at 80 ° C. until there are no free ones NCO groups are more detectable (titration). For neutralization 12.6 g of triethylamine are worked in well.

After adding 622 g of deionized water within 5 minutes a finely divided aqueous polyurethane dispersion is obtained.

Production Example 7: a) Preparation of a carboxy-functional epoxy group-containing polymers:

x = 1 bis 8 die in 108 g Xylol bei 50°C homogenisiert worden waren, innerhalb 1 Stunde zugetropft. Bei 90°C wurde so lange gerührt, bis das Reaktionsgemisch eine Säurezahl in Wasser von 165 (100 %iges Harz) erreicht hatte. Danach wurden 12 g Wasser zugemischt und nach 6-stündigem Rühren bei 80 bis 90°C eine Säurezahl in Butanol von 168 (100 %iges Harz) erreicht. Die Gemischtemperatur wurde auf 60°C gesenkt und nach Zugabe von 0,3 g Lithiumbenzoat 132 g eines epoxydierten Leinöls (Epoxidzahl = 8,7) innerhalb von 2 Stunden zugetropft und die Mischung so lange gerührt, bis die Säurezahl in Butanol auf 86,5 abgesunken war. Anschließend wurde eine Mischung von 42 g Dimethyl-amin (60 %ig in Wasser) in 860 g Wasser eingerührt. Es wurde eine hellgelbe, opaleszierende Lösung erhalten, aus der bei 0,1 bar und 40°C das organische Lösungsmittel abdestilliert wurde. Nach Filtration wurde eine gelbliche, praktisch klare wäßrige Harzlösung erhalten. Festkörpergehalt: 32 % (1 Stunde bei 125°C).In a solution of 141 g of a polyester (OHZ = 88), prepared on the basis of phthalic anhydride, isophthalic acid, maleic anhydride, propanol and glycerol, as described in DE-OS 28 11 913, in 70 g of methyl ethyl ketone, 100 g of an anhydride mixture (SZ / H ₂ O = 486), prepared by reacting trimellitic anhydride with 1,2-propanediol, thus consisting of trimellitic anhydride and anhydrides of the formulas below

x = 1 to 8 which had been homogenized in 108 g of xylene at 50 ° C. were added dropwise within 1 hour. The mixture was stirred at 90 ° C. until the reaction mixture had reached an acid number in water of 165 (100% resin). Thereafter, 12 g of water were mixed in and, after stirring for 6 hours at 80 to 90 ° C., an acid number in butanol of 168 (100% resin) was reached. The mixture temperature was reduced to 60 ° C. and, after adding 0.3 g of lithium benzoate, 132 g of an epoxidized linseed oil (epoxy number = 8.7) were added dropwise over the course of 2 hours, and the mixture was stirred until the acid number in butanol reached 86.5 had sunk. A mixture of 42 g of dimethylamine (60% in water) was then stirred into 860 g of water. A light yellow, opalescent solution was obtained, from which the organic solvent was distilled off at 0.1 bar and 40 ° C. After filtration, a yellowish, practically clear, aqueous resin solution was obtained. Solids content: 32% (1 hour at 125 ° C).

b) Preparation of the polymer dispersion

In a reactor equipped with a stirrer, reflux condenser, Internal thermometer and metering device for the monomers, as well as the Initiator, 705 g of the above aqueous (32%) Dispersion and 196 g of water filled. This mixture was under Stirring heated to 80 ° C and a solution of 0.5 g Ammonium peroxydisulfate added in 35 g of water. 5 minutes after the 35 g of a monomer mixture of 125 g were added to the initiator Methyl methacrylate, 94 g n-butyl acrylate and 17 g glycidyl methacrylate added and after a further 15 minutes prepolymerization remaining amount of monomer metered in over 2 hours. 10 minutes after A further 0.2 g of ammonium peroxydisulfate, dissolved in 10 g of water, added within 10 minutes and the Batch stirred at 80 ° C for 2 hours to complete conversion achieve. The result was a stable aqueous dispersion with approx. 40 % Solids content.

Production Example 8: a) Preparation of a carboxy-functional epoxy group-containing polymers:

In a solution of 127 g of a polyester (OHZ = 107) in 70 g of methyl ethyl ketone, 100 g of anhydride mixture (SZ / H ₂ O = 560) were prepared by reacting trimellitic anhydride with 1,2-propanediol in 30 g of acetone were homogenized at 50 ° C, added dropwise within an hour. The mixture was stirred at 90 ° C. until the reaction mixture had reached an acid number in water of 197 (based on 100% resin). Then 15 g of water were added. After stirring for 6 hours at 80 to 90 ° C, the acid number in butanol was 180 (100% resin). The mixture temperature was reduced to 60 ° C. and 133 g of an epoxidized linseed oil (epoxy number = 8.9) were added dropwise over the course of 2 hours.

The mixture was stirred until the acid number in butanol had dropped to 90. Then a mixture of 56 g Dimethylaminoethanol stirred in 540 g of water. there has been a get light yellow, opalescent solution from which at 0.1 bar and 40 ° C the organic solvent was distilled off. To Filtration became a yellowish, practically clear aqueous resin solution receive. Solids content (1 h at 125 ° C) approx. 39%.

b) Preparation of the polymer dispersion

355 g of the (39%) aqueous dispersion from 8a) were in one Reactor equipped with a stirrer, reflux condenser, internal thermometer and Metering devices for the monomers and the initiator was equipped, mixed with 452 g of water, the mixture under Stirring heated to 80 ° C and a solution of 0.5 g Ammonium peroxydisulfate added in 35 g of water. 5 minutes after the 35 g of a monomer mixture of 165 g were added to the initiator Methyl methacrylate, 142 g n-butyl acrylate and 24 g hydroxyethyl acrylate added and after a further 15 minutes prepolymerization remaining amount of monomer metered in over 2 hours. 10 minutes after A further 0.2 g of ammonium peroxydisulfate, dissolved in 10 g of water, added within 10 minutes and the Batch stirred at 80 ° C for 2 hours to complete conversion achieve. The result was a stable aqueous dispersion with approx. 40 % Solids content.

Production Example 9: Production of a paste resin

In a reaction vessel with an internal thermometer and a reflux condenser, 1395 g of a linear saturated polyester (built up from adipic acid and hydroxypivalic acid neopentyl glycol ester) with an OH number of 112 and a viscosity (at 25 ° C.) of 8.7 Pas with good stirring with 161 g of dimethylol propionic acid and 163 g of trimethylolpropane heated to 90 ° C to dissolve and then cooled to 50 ° C. After adding 865 g of tetramethylxylylene diisocyanate, the mixture is slowly heated to 120 ° C. until the NCO content is below 0.2%. The mixture is then diluted with 861 g of methoxypropanol. Solid (30 min 150 ° C) 75% by weight Acid number (based on solids) 27 Viscosity at 25 ° C, diluted to 40% with methoxypropanol 210 mPa.s *

A mixture of 58.3 g of dimethylethanolamine and 58.3 g of water is quickly added to 1963 g of this resin solution and heated to 80.degree. Then it is slowly diluted with water to form a cloudy, highly viscous paste that can be easily processed under heat and has the following characteristics: Solids (30 min. 150 ° C) 32.3% by weight Viscosity at 25 ° C 1.3 Pas MEQ value 42 PH value 7.6

Production of the components for the following paint examples Production Example 10:

Preparation of a binder solution
50.00 g of the water-dilutable binder described above under Preparation Example 7 are mixed with 43.94 g demineralized water and 6.00 g Butoxyethanol mixed and with 0.06 g N-Dimethylaminoethanol adjusted to a pH of 6.2-6.4.

Production Example 11:

Production of an aluminum slope
20.50 g of a commercially available aluminum paste with a metal content of 65% are mixed with 7.00 g Butoxyethanol and 15.50 g demineralized water well mixed and then mixed with 4.00 g the above under Production Example 7 and additionally 4.50 g the binder described in Production Example 2, 10.00 g butoxyethanol, 34.70 g demineralized water and 3.00 g a commercially available acidic acrylate thickener. With a mix of 0.08 g N-dimethylaminoethanol and 0.72 g demineralized water is adjusted to a pH of 6.2 - 6.4.

Production example 12:

Production of a blue pigment grind
With the help of a dissolver 10.00 g Cu phthalocyanine pigment in 17.00 g a commercially available hexamethoxymelamine resin and 10.00 g Predispersed butoxyethanol and after the addition of others 5.00 g of melamine resin and 10.00 g Dispersed butoxyethanol with a bead mill. After that, mix with 0.90 g a commercial acidic acrylic thickener and 18.91 g deionized water and with 2.00 g N-dimethylaminoethanol and 26.19 g demineralized water adjusted to pH 7.1 - 7.3.

Production Example 13:

Production of a green pigment grind 20.00 g of a chlorinated phthalocyanine pigment are mixed with a dissolver 20.00 g the binder described above under Preparation Example 9, 35.00 g Butoxyethanol and 0.50 g Predispersed N-dimethylaminoethanol and then dispersed it on a bead mill. Then the mixture with 24.50 g deionized water.

Production example 14:

The procedure was as described in Production Example 10, however using that described in Production Example 8 Binder (50.00 g).

Production Example 15:

The procedure was as described in Preparation 11, however using that described in Production Example 8 Binder (4.00 g), together with that under preparation example 2 described binder (4.50 g).

Examples of paint formulations example 1 1.1 Production of a water-thinnable, blue metallic basecoat

30.00 g of the binder solution described in Preparation Example 10 are included 19.00 g the aluminum slope described in Production Example 11, 1.90 g acidic acrylate thickener (as used above), 17.44 g demineralized water and 0.25 g N-Dimethylaminoethanol stirred for 30 minutes.

In this mix 25.50 g the polyurethane dispersion described in Preparation 6 stirred in and the pigment grind described in Preparation 12 is in an amount of 0.94 g added. Then, with stirring 4.00 g n-Butanol added and with 0.96 g Water adjusted to a viscosity of 90 - 95 mPa.s at a shear rate of 100 sec ^-1 . Solids content: 18.0% by weight (120 minutes in a forced-air drying oven at 120 ° C).

1.2 Apply the basecoat and a clearcoat

In a usual way with Zn phosphating, electrocoat and The primer described in 1.1 becomes the base coat that has been pre-coated with spray paint applied with a compressed air atomizing spray gun so that in two application layers a total dry film thickness of 15 microns is achieved. The conditions for applying the basecoat are 23 ° C ambient temperature and 60% relative humidity. After The coated tin is applied in a forced air drying oven 5 Forced minutes at 50 ° C dried and after cooling to 23 ° C in usually with a commercially available acrylic melamine resin clear coat layered and baked at 130 ° C for 30 minutes.

You get a uniform cloud-free coating with a excellent metallic effect, very high gloss and excellent Resistance to condensation.

Example 2 2.1 Production of a water-dilutable silver-colored Metallic base coat

Analogously to Example 1.1, a silver-colored basecoat is produced from 40.00 g the binder solution described in Preparation Example 14, 19.00 g the aluminum slope described in Production Example 15, 1.90 g acidic acrylate thickener, 0.26 g N-dimethylaminoethanol, 22.00 g Polyurethane dispersion (according to preparation example 2), 4.00 g n-butanol and 12.84 g demineralized water.

The solids content is 18.0% by weight (120 minutes in a forced-air drying oven at 120 ° C). The viscosity is 90 - 95 mPa.s with a shear rate of 100 sec ^-1 .

2.2 Apply the basecoat and a clearcoat

As described in Example 1.2, a pre-coated sheet is used Basecoat coated and forced drying at 50 ° C for 5 minutes. To cooling with a commercially available two-component acrylic isocyanate clearcoat layered and baked at 130 ° C for 30 minutes.

The coating obtained in this way is characterized by high brilliance, absolutely even cloud-free effect formation, pronounced Metallic effect and excellent resistance to condensation.

Example 3 3.1 Production of a water-thinnable green metallic basecoat

The basecoat is made from analogy to Example 1.1 59.00 g Binder solution according to production example 10 18.50 g Aluminum slope according to production example 11 1.90 g acidic acrylate thickener, 0.26 g N-dimethylaminoethanol, 4.80 g Polyurethane dispersion according to preparation example 4 0.60 g the green pigment grind described in Preparation Example 13, 4.00 g n-butanol and 10.94 g demineralized water. Solids content 17.1% by weight (120 minutes in a convection oven at 120 ° C), viscosity 90 - 95 mPa.s at a shear rate of 100 sec ^-1 .

3.2 Apply the basecoat and a clearcoat

As described in Example 1.2, the basecoat from 3.1 is applied to one pre-coated sheet and applied after the forced drying overlaid with a commercially available acrylic melamine clear coat and at Baked at 130 ° C for 30 minutes. The result is a green one Metallic coating with the same good properties as in the Examples 1.2 and 2.2.

Example 4 4.1 Production of a plain-colored, red basecoat

300 g of a conventional paste resin (according to the example from DE-OS 4 000 889) are mixed with 350 g of a commercially available vat pigment (Color Index Red 168) mixed. With dimethylethanolamine to pH 8.5 and through Addition of deionized water to a solids content of 50% by weight set. Then it is dispersed transparently in a bead mill.

4.2

1.4 g of a commercially available thickener based on polyacrylic acid (solids: 10% by weight, pH 7.5) are mixed with 129 g of the dispersion from Example 1 and 40 g of the paste resin from Example 4.1. 24 g of a commercially available, water-insoluble melamine resin (Setamine US 138 / BB 70 from AKZO) are then added with stirring. Then 10 g of the red paste from Example 4.1 are added and stirred in homogeneously. With deionized water, an application viscosity of 100-130 mPa.s, measured by rotational viscometry, is set at a shear rate of 231 sec ^-1 and at 25 ° C.

4.3 Applying the basecoat and a clearcoat

The waterborne basecoat obtained is applied to a conventional, phosphated and by cathodic dip painting and pre-coated with filler Body panel applied by spraying. This happens in one Dry film thickness of 30 µm. After the application, at Room temperature flashed off for 10 minutes and then at 10 minutes Pre-dried at 80 ° C. Then a commercial, melamine-curing car series clear lacquer on acrylic resin base in one Dry layer thickness of 35 µm overcoated and 18 minutes at 120 ° C (Object temperature) dried.

A multi-layer coating with excellent resistance to condensation water is obtained (DIN 50 017, 240 hours, 40 ° C).

Example 5

Production of a silver-metallic two-layer paint
20 g of a commercially available aluminum paste suitable for waterborne basecoat with 65% by weight of aluminum, 20 g of butylglycol, 6 g of N-methylpyrrolidone and 1 g of a commercially available wetting agent are mixed together for the bronze digestion. 1.4 g of a commercially available thickener based on polyacrylic acid (solids: 10% by weight, pH 7.5) are then mixed in. Thereafter, 129 g of the dispersion from Example 1 and 40 g of the paste resin from Example 4.1 are stirred into the bronze digestion.

24 g of a commercially available, water-insoluble melamine resin (Setamine US 138 / BB 70 from Akzo) are then added with stirring. With deionized water, an application viscosity of 100-130 mPa.s, measured by rotational viscometry, is set at a shear rate of 231 s ^-1 and at 25 ° C.

The waterborne basecoat obtained is applied to a conventional, phosphated and by cathodic dip painting and pre-coated with filler Body panel applied by spraying. This happens in one Dry film thickness of 15 µm. After the application, at Room temperature flashed off for 10 minutes and then at 10 minutes Pre-dried at 80 ° C. Then a commercial, melamine-hardening car series clear lacquer on acrylic resin base in one Dry layer thickness of 35 µm overcoated and 18 minutes at 120 ° C (Object temperature) dried.

A multi-layer coating with excellent durability is obtained against condensation.

Claims (9)

1. Method of producing a decorative multilayer lacquer coating on a metal substrate by electrophoretic application of a primer layer, application of a filler layer, application of a colour- and/or effect-giving base lacquer layer from an aqueous, polyurethane-containing base lacquer, and covering with a transparent lacquer layer, characterised in that the base lacquer used is an aqueous self-crosslinking coating composition containing as binder an aqueous polyurethane resin dispersion based on a polyurethane resin that is linear or branched in structure and has a number-average molar mass (Mn) of from 2500 to 120,000, a content of from 10 to 400 mmol of lateral and/or terminal silicon-bonded hydroxyl and/or R'O groups, wherein
   R' = C₁- to C₈-alkyl or C(O)R''' and
   R''' = C₁- to C₁₀-alkyl,
   per 100 g of solid resin, a hydroxyl number of from 0 to 150 mg KOH/g, based on solid resin, silicon-bonded hydroxyl groups not being included in the calculation of the OH number, and a content of ionic groups, groups that can be converted into ionic groups, and/or hydrophilic groups of from 5 to 200 mEqu per 100 g of solid resin.
2. Method according to claim 1, characterised in that the polyurethane resin has a content of from 20 to 300 mmol of lateral and/or terminal silicon-bonded hydroxyl and/or R'O groups.
3. Method according to any one of the preceding claims, characterised in that the aqueous polyurethane resin dispersion contained as binder is obtainable by reacting a linear or branched, non-gelled, isocyanate-functional polyurethane prepolymer containing ionic groups, groups capable of ion formation and/or hydrophilic groups, with one or more compounds of the general formula ((H-X-)_nR)_aSi(OR')_b(R")_c wherein X = O, S, NH or NR'^v,
   R = a bifunctional, trifunctional or tetrafunctional organic radical having a molecular weight of from 13 to 500,
   R' = C₁- to C₈-alkyl or C(O)R''',
   R'' = R''' = C₁- to C₁₀-alkyl,
   R'^v = C₁- to C₈-alkyl,
   a = 1, 2 or 3,
   b = 1, 2 or 3,
   c = 0, 1 or 2,
   n = from 1 to 3,
   wherein a plurality of radicals R', R'' and R''' may be identical or different and wherein the sum of a plus b plus c is four,
   optionally in admixture with one or more alkanolamines carrying NH₂ and/or NH groups and having an OH functionality of at least 1,
   and converting the optionally neutralised reaction product into an aqueous dispersion by mixing it with water in a more than ten times stoichiometric excess of the amount of water necessary for hydrolysis of the R'OSi groups.
4. Method according to claim 3, characterised in that the isocyanate-functional polyurethane prepolymer is obtainable by reacting, in an anhydrous medium,

   a) at least one linear or branched compound that carries at least two groups reactive towards isocyanate and has a mean molecular weight of from 60 to 10,000,

   b) at least one organic polyisocyanate,

   c) at least one compound that has more than one group reactive with isocyanate, and at least one ionic group, group capable of ion formation and/or hydrophilic group, and that has a number-average molar mass (Mn) of up to 10,000, in an NCO/OH ratio greater than from 1 to 4 : 1.
5. Method according to claim 4, characterised in that the linear or branched compound of component a) is at least one polyol based on one or more polyethers, polyesters, polyurethanes and/or polycarbonates, having at least two OH groups in the molecule and a number-average molar mass (Mn) of from 60 to 10,000, optionally with the concomitant use of one or more at least difunctional low molecular weight alcohols and/or amines and/or amino alcohols different therefrom and having a molar mass below 600.
6. Method according to any one of the preceding claims, characterised in that the aqueous coating compositions for the base lacquer layer contain one or more different self-crosslinking binders or binders that crosslink by external means in an amount of from 0 to 75 wt.%, based on the total resin solids.
7. Method according to any one of the preceding claims, characterised in that the aqueous coating compositions for the base lacquer layer have a solids content of from 10 to 50 wt.% with a ratio of pigment to binder plus optionally present crosslinking agent and paste resin of from 0.03 : 1 to 3 : 1, in each case based on the weight of the solids.
8. Method according to any one of claims 1 to 7, characterised in that the aqueous base lacquer layer is applied in a dry layer thickness of from 8 to 50 µm and, after a phase of exposure to air, is covered by the wet-on-wet method with a conventional clear lacquer in a dry layer thickness of from 30 to 60 µm and is dried together therewith at from 20 to 150°C.
9. Method according to any one of claims 1 to 8, characterised in that it is carried out for the multilayer lacquering of motor vehicles.